HETEROGENEITY OF THE BINDING SITES OF BOVINE SERUM ALBUMIN
HETEROGENEITY OF THE BINDING SITES OF BOVINE SERUM ALBUMIN
复制标题
DOI：
10.1021/ja01162a099
复制
发表时间：
1950-01-01
影响因子：
15
通讯作者：
KARUSH, F
中科院分区：
文献类型：
--
作者：
KARUSH, F
阴离子偶氮染料对- 2-羟基-5-m的可逆结合。用结晶牛血清白蛋白（Armour and Company）测定了乙基苯基偶氮苯甲酸。在25[度]和5[度]C下，用平衡透析法测定蛋白质浓度。3.00 x 10-5[图像]。这些数据符合这样的假设，即每个蛋白质分子有22个染料结合位点，这些位点被分为两个不同的组。第I组由每个蛋白质分子约5个位点组成，具有相对较大的结合常数，第II组约有17个位点，对染料的亲和力要小得多。测定与两组药物结合的[DELTA]F[度]、[DELTA]H[度]、[DELTA]S[度]值。两组数据的比较表明，结合常数的差异几乎完全是由于与结合过程相关的熵变的差异造成的。甲苯和氯离子明显抑制结合；0.5%的牛γ -球蛋白则没有。由于血清白蛋白与不同构型的分子具有竞争性结合，因此假设这些蛋白能够以多种近似的分子构型存在于血浆中。能量相等，处于热力学平衡。讨论了半抗原白蛋白结合与半抗原抑制研究的定量意义的关系。
The reversible binding of the anionic azo dye, p-(2-hydroxy-5-m.ethylphenylazo)-benzoic acid by crystallized bovine serum albumin (Armour and Company) was detd. at 25[degree] and 5[degree]C by the method of equilibrium dialysis at protein concn. of 3.00 x 10-5[image]. The data fitted the assumption that there are 22 dye-binding sites per protein molecule and that these are divided into 2 distinct groups. Group I consists of about 5 sites per protein molecule with a relatively large binding constant and group II of about 17 sites with a much smaller affinity for the dye. The values of [DELTA]F[degree], [DELTA]H[degree] and [DELTA]S[degree] for the binding to the 2 groups were detd. Comparison of the data for the 2 groups reveals that the divergence in the binding constants is almost entirely due to the difference in the entropy change associated with the binding process. Toluene and chloride ion significantly inhibit binding; 0.5% bovine gam ma-globulin does not. Since the serum albumins bind molecules with diverse configurations competitively, it is postulated that these proteins have the ability to exist in soln. in many molecular configurations of approx. equal energy and in thermodynamic equilibrium with each other. The relationship of albumin binding of haptens to the quantitative significance of recent hapten inhibition studies is discussed.